The present invention relates generally to network communications. More specifically, the present invention relates to a network cable socket (or plug) that is integrated with a chip carrier and associated circuitry.
Communication between computers and network devices typically occurs over cables that are connected to a hardware device using a pair of male and female connectors. A cable is typically terminated at each end by a male plug (or connector) which connects to a female jack (or socket) mounted on a printed circuit board or within a hardware device.
FIG. 1 illustrates a prior art network interface card (NIC) 10 that includes a jack 16 and supporting circuitry. Network interface card 10 is used to interface analog signals from a network cable to a computer. In this example, NIC 10 is an Ethernet card. Shown is an Ethernet communications cable 12 terminating in an RJ-45 plug 14. Plug 14 mates with RJ-45 jack 16 which is mounted on NIC 10. Also mounted on NIC 10 is a variety of analog circuitry 18 which is in communication with jack 16 and with a transceiver integrated circuit 20.
Jacks such as RJ-45 jack 16 are known in the art. Jack 16 may also include electromagnetic shielding around its plastic casing to shield the internal connections from outside circuitry and vice-versa. Some RJ-45 jacks also include a coil and/or LEDs within the jack itself.
Analog circuitry 18 includes discrete components such as inductance coils, resistors and capacitors, all which are useful in the processing of the analog signal over cable 14. Transceiver 20 is a known device that performs low-level processing of a communications signal. Transceiver 20 includes A/D and D/A converters and other related circuitry. By way of example, transceiver 20 is an Intel 82555 device. Media access controller (MAC) integrated circuit 22 is also a known device that performs high level processing of the communications signal and is in communication with transceiver 20 and a computer bus interface 24. MAC 22 provides the high-level interface to the computer bus and to the computer software. By way of example, MAC 22 is an Intel 82557 device. Computer bus interface 24 is an interface from NIC 10 to a computer bus of the computer into which it is inserted. By way of example, interface 24 connects to a PCI bus, a VME bus, and the like. Not shown on NIC 10 is other circuitry such as a microprocessor, boot PROM, memory, etc.
NIC 10 illustrates an example of how a computer (or other hardware device) interfaces to a network communications cable (such as an Ethernet cable). As can be seen from FIG. 1, the interface requires not only jack 16, but also discrete analog components 18, and two separate integrated circuits 20 and 22, all of which are spread out over a substantial portion of NIC 10.
Although able to operate correctly, such a design has a number of inherent drawbacks. Primarily, the physical separation of the various components from jack 16 leads to noise, impedance and radiation difficulties. For example, jack 16 may be separated from analog components 18, transceiver 20, and MAC 22 by a number of inches. This separation allows noise to interfere with the analog signal and requires that a board designer make allowances for the noise. In addition, because signals are traveling over relatively large distances on metal traces on NIC 10, there is a greater problem with electromagnetic radiation. Not only is there a problem with electromagnetic radiation being received from other hardware on the card and from within the computer, but also components 16-22 produce a certain amount of electromagnetic radiation themselves. The fact that they are physically separated only aggravates the noise and radiation problems. Because radiation is produced, any such design of a NIC 10 must comply with FCC regulations. Also, because jack 16 is separate from transceiver 20, a designer must also match the impedance between the two, thus requiring extra work and increase cost for the designer.
Because of the separation of all these components, a manufacturer of a transceiver 20 and/or a MAC 22 is required to provide specifications for these devices which includes the resistors, capacitors and coils needed. The integrated circuit manufacturer must also provide specifications for optimal distances to jack 16, locations for the discrete components, etc. Even after supplying all of these specifications, a manufacturer who has produced a high quality transceiver 20 or MAC 22 must still rely upon a board manufacturer to abide by all of the specifications and to correctly design the placement of components and the routing of signals on a device such as NIC 10. If a board manufacturer fails to follow specifications or does not allow for noise, impedance matching, electromagnetic radiation, etc., such a NIC 10 will not function properly with a network communications cable even though the best efforts of an integrated circuit manufacturer has produced a properly functioning transceiver 20 and media access controller 22.
Another drawback to having various components on NIC 10 separated by relatively large distances is that the communications protocol being used may not be able to operate at as high a speed as desired. For example, although the current standard for Ethernet communications uses a 100 Mbits/sec rate, it is more difficult to achieve higher speeds using a network interface card that has higher noise, higher inductance and higher capacitance. Furthermore, excess noise over a network communication cable means that the cable""s length is limited. Because the signal attenuates over a lengthy cable, introduction of noise on the cable from a network interface card would make a relatively weak signal on a longer cable hard to detect at the other end.
Other prior art techniques attempt to address this separation of components problem but each have their own drawbacks involving complexity, size, cost, etc. One technique uses a multi-chip module. In one variation, both the transceiver and MAC dies are placed into one package.
Although this technique results in the transceiver and MAC being closer to one another, it is still an expensive technique. And even though the transceiver and MAC are within the multi-chip module, the necessary resistors, capacitors and coils are still mounted outside the package. Having the components external to the package means that their sizes and locations must be specified and there is the possibility of excess noise and electromagnetic interference. As discussed above, a manufacturer of such a multi-chip module must still rely upon a board designer to use the correct discrete components and to place them correctly. In addition, such a multi-chip module has a great number of output pins and appears to the external world as two devices; thus more space is taken up and the module is more costly to use.
Furthermore, because the transceiver incorporates both digital and analog technology, the geometry used for manufacturing the transceiver is constrained by limitations on miniaturization of analog technology. For example, currently analog geometry lags behind the miniaturization of digital technology. Analog geometry is down at the 0.5 to 0.8 micron size, while digital geometry is down to the 0.25 micron size and below. Because the transceiver incorporates both digital and analog technology, a single process used to manufacture the transceiver uses the larger analog geometry. Such a larger geometry is inefficient for digital technology.
Use of analog geometry sizes for a transceiver that incorporates a high percentage of digital technology means that such a transceiver cannot be made as small as desired. As digital technology takes up more of a percentage of a transceiver, this presents a problem. For example, in the early days of Ethernet a transceiver chip communicating using 10Base5 protocol (10 Mbits/sec) was mostly all analog technology and included about 100 gates total. Thus, the small amount of digital technology (if any) that had to be produced using an analog process geometry was not a large problem. As more and more digital technology is used in a transceiver, and the gate count increases, it becomes problematic if the digital technology within the transceiver must be produced using a larger analog geometry. For example, current Ethernet transceivers using 100BaseTX (100 Mbits/sec) protocol are approximately 50% digital technology and have a substantial number of gates. It is projected that the upcoming gigabit Ethernet technology (1000BaseT) will be 90% digital technology and will have approximately 700,000 gates.
With this relatively large number of gates, suddenly the size of the gates is very significant. If such a transceiver were manufactured using an analog geometry of 0.5 microns, it would likely be too large and too expensive for all practical purposes. A more advanced analog geometry of 0.22 microns could be attempted, but this in itself would be risky and expensive. Thus, even though one technique places both a transceiver and a MAC into a multi-chip package, the transceiver itself cannot be made as small as desired because it is constrained by the size of the analog geometry that can be used. It is possible to use both a larger analog geometry process and the smaller digital geometry process on a single die, but this procedure is complex and expensive. For cost reasons, it can be prohibitive to use two different processes to manufacture a single die.
A second technique available is to use a hybrid device implemented with thick film technology to place one or more dies into one package. Hybrid technology has some advantages in that a transceiver die and a MAC die placed into such a package may be wired directly together, and any needed resistors and capacitors can be mounted close to the devices inside the hybrid package. A lead frame surrounding the hybrid package connects the devices within to the outside world. Unfortunately, hybrid technology uses a ceramic or printed circuit board substrate which is extremely expensive. Such a substrate does not dissipate heat well, which can lead to overheating problems. Also, a hybrid package can be relatively large, has a large number of output pins and is unable to incorporate an inductance coil within it. Any needed coils must still be mounted external to the hybrid device and at such a distance that may cause some of the noise problems described above.
A third technique in use is to incorporate both the transceiver and the MAC into a single integrated circuit die. Termed a mixed-signal design, such a die incorporates both the analog and digital technology of the transceiver and the MAC. One example of such a die is the Intel 82558 device. Such a device is relatively large and suffers from some of the same drawbacks as the multi-chip package. As described above, because the die incorporates both analog and digital technology, the processing technique used to manufacture the die is constrained by the currently available analog geometry size of about 0.5 to about 0.8 microns. (Currently, a geometry size down to about 0.35 microns is very nearly impossible using analog processing techniques.) It would be possible to use two different processes for manufacturing the die, but this is a complex and expensive undertaking. A further disadvantage to incorporating both a transceiver and a MAC into a single die is that both the analog functionality and the digital functionality share a common ground and power, thus introducing unwanted noise into the device. Excess noise creates problems at higher communication speeds and for longer lengths of cable.
Older prior art techniques have used two separate integrated circuits, one incorporating an analog transceiver and the other incorporating the digital functionality of the MAC. Although this technique would separate analog and digital functionality (thus allowing for different processes to be used for each device), the two devices would still be separated by a relatively large distance when mounted on a board. Separating an analog device from a digital device in this form would require more space on a board and would also add inductance to the system.
Another issue with existing jacks is their size. The amount of board space taken up by the jack and associated circuitry affects price and design complexity. It is generally desirable to have a higher board density. Jack 16 may also include two optional light-emitting diodes (LEDs) that are found in the upper portion of the face of the jack to the sides. These LEDs help monitor the transceiver status, but as they are bulky, they increase the width of the jack to greater than its standard size. In an environment such as a network switch where a large number of jacks may be mounted one adjacent to another, this slight increase in the size of each jack means that a larger portion of a printed circuit board is used up. The use of electromagnetic shielding around a jack also increases its width.
Therefore, it would be desirable to have an apparatus that places in close proximity a socket connector (or a plug connector), an integrated circuit and associated circuitry to address the above drawbacks. It would be further desirable for such an apparatus to be inexpensive to manufacture and easier for designers to incorporate into their network communication designs. It would be also desirable to implement a socket (or plug) that maintained its minimal, standard width while at the same time providing monitoring LEDs and appropriate shielding.
To achieve the foregoing, and in accordance with one purpose of the present invention, an integrated module is disclosed that incorporates not only a cable socket, but also a chip carrier for an integrated circuit and a daughter card for discrete components. In an alternative embodiment, an integrated module incorporates a cable plug and a chip carrier for an integrated circuit. The present invention provides a simple, elegant solution in an all-in-one package that provides numerous advantages: a single integrated module improves the quality and reduces the cost for a network interface.
In one aspect of the invention, an entire network interface card is contained within an integrated module that is about the same width and height of a standard socket and slightly longer. Alternatively, instead of the integrated module including a socket, the module integrates a plug of a network cable along with a chip carrier. The module does not require a slot in a computer mother board and can be mounted conveniently on any printed circuit board, within a switch, router, hub or other network device. The module may also be mounted on any device that does not have room for a standard network interface card, such as a laptop computer, a hand-held device (personal digital assistant, etc.), instrumentation, etc. The module may even be mounted external to a computer, or in a wall socket.
Integrating a socket, chip carrier and daughter card within one module provides numerous advantages. Because the integrated module is very compact (compared to prior art transceivers and discrete components that may be spread out over a network interface card), the present invention saves space on a printed circuit board and allows more room for other components. Also, because the distance between the socket, the transceiver and its associated resistors, bypass capacitors, noise filtering capacitors and coils is extremely small, noise and impedance problems are negligible. In one aspect of the invention, the resistors, capacitors and coils are grounded as closely as possible to the bonding pads of an associated integrated circuit. Thus, noise is reduced and impedance matching is not needed. Furthermore, because connections to and from the socket, transceiver and discrete components are not spread out over a network interface card, the module picks up far less noise from surrounding components. Similarly, the module itself generates far less electromagnetic radiation of its own.
The reduction in noise picked up by the module and the lowered inductance and capacitance of the unit has advantages for the network communications signal itself. The integrated module can operate at much higher speeds and with greater accuracy. In addition, because there is less noise and distortion of a communication signal, a weaker signal can be picked up (or transmitted) by another transceiver at greater distances, meaning that longer network cables can be used with the present invention.
In one specific embodiment of the present invention, the functionality contained within both the transceiver and the media access controller (MAC) are split into a digital portion and an analog portion. Each of the digital and analog functionality is then implemented on a separate integrated circuit and both integrated circuits are placed next to one another in the chip carrier within the integrated module. Advantageously, the two dies are placed immediately adjacent to one another to decrease the distance between the analog and digital portions. By integrating the chip carrier directly behind the socket and by mounting a daughter card containing discrete components directly above the chip carrier, all of the components necessary for a network connection are placed in extremely close proximity thus providing the advantages discussed herein.
As network interface devices such as transceivers and MACs incorporate more and more digital logic and hundreds of thousands of gates, it is advantageous to separate digital functionality onto one integrated circuit that can be made as small as possible. Also, by avoiding a hybrid design, costs are dramatically lowered and discrete components can still be placed extremely close to the integrated circuits by use of a daughter card mounted directly above them. In a further improvement over a hybrid design, an expensive substrate (such as ceramic or PCB) is not required. The base of the chip carrier is simple metal; each die is mounted to the metal base and electrically connected to one another, as well as each die having bonding wires connected to external pins on the chip carrier. The complexities of a hybrid design in which dies and discrete components are mounted together on a single substrate are avoided.
Furthermore, because the two dies are wired together within a single chip carrier, the external pin count is greatly reduced as compared to a traditional multi-chip package. In a specific aspect of this embodiment, pins from the digital integrated circuit are bonded directly to pins from the analog integrated circuit with which they need to communicate. Further, the dies are designed such that these digital pins are close to the edge of the digital integrated circuit that is adjacent to the analog circuit, and vice-versa. In addition, implementing digital and analog technology on separate integrated circuits allows each device to have its own power and ground thus reducing noise.
In an optional embodiment of the present invention, standard shielding around a network socket is extended to surround the entire integrated module thus providing shielding for not only the socket, but also for the chip carrier and the discrete components on a daughter card. Such shielding provides protection from external noise and also prevents electromagnetic radiation from the internal components from leaking to the outside. Advantageously, such a shielded integrated module provides a compact network connection on any printed circuit board or network device that might be sensitive to electromagnetic radiation. In a further aspect of this embodiment, the metal shielding extends underneath the integrated module and contacts the copper base of the chip carrier thus allowing the surrounding metal shield to also serve as a heat sink for the chip carrier and internal components.
In a further aspect of this embodiment, any number of integrated modules may be ganged together (placed immediately adjacent to one another) and a single electromagnetic shield placed around all of the integrated modules. Thus, shielding is provided for all modules and the total width of the adjacent modules is reduced because a single shield is used to surround all modules. Having individual shields for each module would increase the overall width of the ganged unit and thus decrease valuable board space. To further decrease the width of an integrated module and provide more board space, a light pipe is used in conjunction with the socket instead of traditional light-emitting diodes (LEDs). A traditional RJ-45 socket incorporates LEDs into the upper outside portions of its face, thus increasing the width of the socket over its standard size because of the bulk of the LEDs. Advantageously, one aspect of the present invention mounts the LEDs on a daughter card behind the socket and uses a narrower light pipe to route light from an LED up to the face of the socket. Using this technique, monitoring lights are provided yet the socket may be kept to its minimal possible width.
In another embodiment of the invention, a chip carrier by itself has pins bent both downward to attach to a printed circuit board and upward to attach to an above daughter card. By providing a chip carrier with pins bent in both directions, a daughter card may be manufactured separately from the chip carrier and then attached later. In this embodiment, a manufacturer of integrated circuits is able to concentrate their expertise on chip making; finished chips are mounted within the chip carrier. The manufacturer of daughter cards is able to concentrate their expertise on the assembly of printed circuit boards. Either manufacturer or a third party may then assemble both finished products, the chip carrier containing chips and the daughter card, in a simple fashion. Advantageously, the chip carrier of this embodiment facilitates this division of labor and ease of assembly by providing a carrier that has pins bent upward to attach to a printed circuit board, and pins bent downward to interface to a particular device such as computer board, network switch, hub, router, etc.
The present invention greatly reduces the costs associated with producing a network connection. By incorporating any number of integrated circuits into a single chip carrier, the number of output pins are reduced and the chip carrier appears to the external world as a single integrated circuit, thus reducing costs. Furthermore, standard processing techniques are used to produce the digital and the analog integrated circuits, thus avoiding high costs associated with multi-chip packages, hybrid devices, and mixed-signal technology. Also, because all components needed for a network connection are integrated into a single package, no extra design need be performed by a system integrator or board manufacturer, thus reducing their costs. In addition, because the integrated module takes up far less board space, it is less expensive to implement in terms of board space used.